scholarly journals Candidate Periodically Variable Quasars from the Dark Energy Survey and the Sloan Digital Sky Survey

2020 ◽  
Author(s):  
Yu-Ching Chen ◽  
Xin Liu ◽  
Wei-Ting Liao ◽  
A Miguel Holgado ◽  
Hengxiao Guo ◽  
...  
Keyword(s):  
Black Holes ◽  
Dark Energy ◽  
Detection Rate ◽  
Sloan Digital Sky Survey ◽  
Light Curves ◽  
Close Binary ◽  
Single Frequency ◽  
Dark Energy Survey ◽  
Sky Survey ◽  
Energy Survey

Abstract Periodically variable quasars have been suggested as close binary supermassive black holes. We present a systematic search for periodic light curves in 625 spectroscopically confirmed quasars with a median redshift of 1.8 in a 4.6 deg2 overlapping region of the Dark Energy Survey Supernova (DES-SN) fields and the Sloan Digital Sky Survey Stripe 82 (SDSS-S82). Our sample has a unique 20-year long multi-color (griz) light curve enabled by combining DES-SN Y6 observations with archival SDSS-S82 data. The deep imaging allows us to search for periodic light curves in less luminous quasars (down to r ∼23.5 mag) powered by less massive black holes (with masses ≳ 108.5M⊙) at high redshift for the first time. We find five candidates with significant (at >99.74% single-frequency significance in at least two bands with a global p-value of ∼7 × 10−4–3× 10−3 accounting for the look-elsewhere effect) periodicity with observed periods of ∼3–5 years (i.e., 1–2 years in rest frame) having ∼4–6 cycles spanned by the observations. If all five candidates are periodically variable quasars, this translates into a detection rate of ${\sim }0.8^{+0.5}_{-0.3}$% or ${\sim }1.1^{+0.7}_{-0.5}$ quasar per deg2. Our detection rate is 4–80 times larger than those found by previous searches using shallower surveys over larger areas. This discrepancy is likely caused by differences in the quasar populations probed and the survey data qualities. We discuss implications on the future direct detection of low-frequency gravitational waves. Continued photometric monitoring will further assess the robustness and characteristics of these candidate periodic quasars to determine their physical origins.

scholarly journals Discovery of a Candidate Binary Supermassive Black Hole in a Periodic Quasar from Circumbinary Accretion Variability

2020 ◽  
Author(s):  
Wei-Ting Liao ◽  
Yu-Ching Chen ◽  
Xin Liu ◽  
A Miguel Holgado ◽  
Hengxiao Guo ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Sloan Digital Sky Survey ◽  
Light Curves ◽  
P Value ◽  
Kinematic Effect ◽  
Dark Energy Survey ◽  
Sky Survey ◽  
Laser Interferometer Space Antenna ◽  
The Look ◽  
Energy Survey

Abstract Binary supermassive black holes (BSBHs) are expected to be a generic byproduct from hierarchical galaxy formation. The final coalescence of BSBHs is thought to be the loudest gravitational wave (GW) siren, yet no confirmed BSBH is known in the GW-dominated regime. While periodic quasars have been proposed as BSBH candidates, the physical origin of the periodicity has been largely uncertain. Here we report discovery of a periodicity (P=1607±7 days) at 99.95% significance (with a global p-value of ∼10−3 accounting for the look elsewhere effect) in the optical light curves of a redshift 1.53 quasar, SDSS J025214.67−002813.7. Combining archival Sloan Digital Sky Survey data with new, sensitive imaging from the Dark Energy Survey, the total ∼20-yr time baseline spans ∼4.6 cycles of the observed 4.4-yr (restframe 1.7-yr) periodicity. The light curves are best fit by a bursty model predicted by hydrodynamic simulations of circumbinary accretion disks. The periodicity is likely caused by accretion rate modulation by a milli-parsec BSBH emitting GWs, dynamically coupled to the circumbinary accretion disk. A bursty hydrodynamic variability model is statistically preferred over a smooth, sinusoidal model expected from relativistic Doppler boost, a kinematic effect proposed for PG1302−102. Furthermore, the frequency dependence of the variability amplitudes disfavors Doppler boost, lending independent support to the circumbinary accretion variability hypothesis. Given our detection rate of one BSBH candidate from circumbinary accretion variability out of 625 quasars, it suggests that future large, sensitive synoptic surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time may be able to detect hundreds to thousands of candidate BSBHs from circumbinary accretion with direct implications for Laser Interferometer Space Antenna.

scholarly journals Extreme Variability Quasars from the Sloan Digital Sky Survey and the Dark Energy Survey

2018 ◽  
Vol 854 (2) ◽  
pp. 160 ◽  
Author(s):  
N. Rumbaugh ◽  
Yue Shen ◽  
Eric Morganson ◽  
Xin Liu ◽  
M. Banerji ◽  
...  
Keyword(s):  
Dark Energy ◽  
Sloan Digital Sky Survey ◽  
Dark Energy Survey ◽  
Sky Survey ◽  
Extreme Variability ◽  
Energy Survey

scholarly journals C iv black hole mass measurements with the Australian Dark Energy Survey (OzDES)

2019 ◽  
Vol 487 (3) ◽  
pp. 3650-3663 ◽  
Author(s):  
J K Hoormann ◽  
P Martini ◽  
T M Davis ◽  
A King ◽  
C Lidman ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Energy ◽  
Emission Line ◽  
Galaxy Evolution ◽  
Supermassive Black Holes ◽  
Black Hole Mass ◽  
Mass Measurements ◽  
Dark Energy Survey ◽  
Energy Survey

ABSTRACT Black hole mass measurements outside the local Universe are critically important to derive the growth of supermassive black holes over cosmic time, and to study the interplay between black hole growth and galaxy evolution. In this paper, we present two measurements of supermassive black hole masses from reverberation mapping (RM) of the broad C iv emission line. These measurements are based on multiyear photometry and spectroscopy from the Dark Energy Survey Supernova Program (DES-SN) and the Australian Dark Energy Survey (OzDES), which together constitute the OzDES RM Program. The observed reverberation lag between the DES continuum photometry and the OzDES emission line fluxes is measured to be $358^{+126}_{-123}$ and $343^{+58}_{-84}$ d for two quasars at redshifts of 1.905 and 2.593, respectively. The corresponding masses of the two supermassive black holes are 4.4 × 109 and 3.3 × 109 M⊙, which are among the highest redshift and highest mass black holes measured to date with RM studies. We use these new measurements to better determine the C iv radius−luminosity relationship for high-luminosity quasars, which is fundamental to many quasar black hole mass estimates and demographic studies.

scholarly journals The mystery of photometric twins DES17X1boj and DES16E2bjy

2020 ◽  
Vol 494 (4) ◽  
pp. 5576-5589 ◽  
Author(s):  
M Pursiainen ◽  
C P Gutiérrez ◽  
P Wiseman ◽  
M Childress ◽  
M Smith ◽  
...  
Keyword(s):  
Dark Energy ◽  
Light Curve ◽  
Spiral Galaxy ◽  
High Velocity ◽  
Photometric Data ◽  
Light Curves ◽  
Curve Evolution ◽  
Physical Origin ◽  
Dark Energy Survey ◽  
Energy Survey

ABSTRACT We present an analysis of DES17X1boj and DES16E2bjy, two peculiar transients discovered by the Dark Energy Survey (DES). They exhibit nearly identical double-peaked light curves that reach very different maximum luminosities (Mr = −15.4 and −17.9, respectively). The light-curve evolution of these events is highly atypical and has not been reported before. The transients are found in different host environments: DES17X1boj was found near the nucleus of a spiral galaxy, while DES16E2bjy is located in the outskirts of a passive red galaxy. Early photometric data are well fitted with a blackbody and the resulting moderate photospheric expansion velocities (1800  km s−1 for DES17X1boj and 4800  km s−1 for DES16E2bjy) suggest an explosive or eruptive origin. Additionally, a feature identified as high-velocity Ca ii absorption ($v$ ≈ 9400 km s−1) in the near-peak spectrum of DES17X1boj may imply that it is a supernova. While similar light-curve evolution suggests a similar physical origin for these two transients, we are not able to identify or characterize the progenitors.

scholarly journals The Milky Way’s total satellite population and constraining the mass of the warm dark matter particle

2018 ◽  
Vol 14 (S344) ◽  
pp. 109-113 ◽  
Author(s):  
Oliver Newton ◽  
Marius Cautun ◽  
Adrian Jenkins ◽  
Carlos S. Frenk ◽  
John C. Helly
Keyword(s):  
Dark Matter ◽  
Dark Matter Particle ◽  
Statistical Error ◽  
Sloan Digital Sky Survey ◽  
Dark Energy Survey ◽  
Satellite Galaxy ◽  
Sky Survey ◽  
Galaxy Luminosity Function ◽  
Energy Survey ◽  
Rule Out

AbstractThe Milky Way’s (MW) satellite population is a powerful probe of warm dark matter (WDM) models as the abundance of small substructures is very sensitive to the properties of the WDM particle. However, only a partial census of the MW’s complement of satellite galaxies exists because surveys of the MW’s close environs are incomplete both in depth and in sky coverage. We present a new Bayesian analysis that combines the sample of satellites recently discovered by the Dark Energy Survey (DES) with those found in the Sloan Digital Sky Survey (SDSS) to estimate the total satellite galaxy luminosity function down to Mv = 0. We find that there should be at least $124_{ - 27}^{ + 40}$ (68% CL, statistical error) satellites as bright or brighter than Mv = 0 within 300 kpc of the Sun, with only a weak dependence on MW halo mass. When it comes online the Large Synoptic Survey Telescope should detect approximately half of this population. We also show that WDM models infer the same number of satellites as in ΛCDM, which will allow us to rule out those models that produce insufficient substructure to be viable.

Statistics, Data Mining, and Machine Learning in Astronomy

2014 ◽  
Author(s):  
Željko Ivezic ◽  
Andrew J. Connolly ◽  
Jacob T VanderPlas ◽  
Alexander Gray
Keyword(s):  
Sloan Digital Sky Survey ◽  
Data Sets ◽  
Complex Data ◽  
Dark Energy Survey ◽  
Astronomical Surveys ◽  
Sky Survey ◽  
Different Types ◽  
Complex Data Sets ◽  
Coding Standards ◽  
Energy Survey

As telescopes, detectors, and computers grow ever more powerful, the volume of data at the disposal of astronomers and astrophysicists will enter the petabyte domain, providing accurate measurements for billions of celestial objects. This book provides a comprehensive and accessible introduction to the cutting-edge statistical methods needed to efficiently analyze complex data sets from astronomical surveys such as the Panoramic Survey Telescope and Rapid Response System, the Dark Energy Survey, and the upcoming Large Synoptic Survey Telescope. It serves as a practical handbook for graduate students and advanced undergraduates in physics and astronomy, and as an indispensable reference for researchers. The book presents a wealth of practical analysis problems, evaluates techniques for solving them, and explains how to use various approaches for different types and sizes of data sets. For all applications described in the book, Python code and example data sets are provided. The supporting data sets have been carefully selected from contemporary astronomical surveys (for example, the Sloan Digital Sky Survey) and are easy to download and use. The accompanying Python code is publicly available, well documented, and follows uniform coding standards. Together, the data sets and code enable readers to reproduce all the figures and examples, evaluate the methods, and adapt them to their own fields of interest.

scholarly journals Superluminous supernovae from the Dark Energy Survey

2019 ◽  
Vol 487 (2) ◽  
pp. 2215-2241 ◽  
Author(s):  
C R Angus ◽  
M Smith ◽  
M Sullivan ◽  
C Inserra ◽  
P Wiseman ◽  
...  
Keyword(s):  
Dark Energy ◽  
Light Curve ◽  
Luminosity Function ◽  
High Redshift ◽  
Absolute Magnitude ◽  
Light Curves ◽  
Evolutionary Time ◽  
Dark Energy Survey ◽  
Monte Carlo Search ◽  
Energy Survey

ABSTRACT We present a sample of 21 hydrogen-free superluminous supernovae (SLSNe-I) and one hydrogen-rich SLSN (SLSN-II) detected during the five-year Dark Energy Survey (DES). These SNe, located in the redshift range 0.220 < z < 1.998, represent the largest homogeneously selected sample of SLSN events at high redshift. We present the observed g, r, i, z light curves for these SNe, which we interpolate using Gaussian processes. The resulting light curves are analysed to determine the luminosity function of SLSNe-I, and their evolutionary time-scales. The DES SLSN-I sample significantly broadens the distribution of SLSN-I light-curve properties when combined with existing samples from the literature. We fit a magnetar model to our SLSNe, and find that this model alone is unable to replicate the behaviour of many of the bolometric light curves. We search the DES SLSN-I light curves for the presence of initial peaks prior to the main light-curve peak. Using a shock breakout model, our Monte Carlo search finds that 3 of our 14 events with pre-max data display such initial peaks. However, 10 events show no evidence for such peaks, in some cases down to an absolute magnitude of <−16, suggesting that such features are not ubiquitous to all SLSN-I events. We also identify a red pre-peak feature within the light curve of one SLSN, which is comparable to that observed within SN2018bsz.

scholarly journals Spectral variability of a sample of extreme variability quasars and implications for the Mg ii broad-line region

2020 ◽  
Vol 493 (4) ◽  
pp. 5773-5787 ◽  
Author(s):  
Qian Yang ◽  
Yue Shen ◽  
Yu-Ching Chen ◽  
Xin Liu ◽  
James Annis ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Sloan Digital Sky Survey ◽  
Spectral Variability ◽  
Dark Energy Survey ◽  
Line Region ◽  
Sky Survey ◽  
Balmer Lines ◽  
Extreme Variability ◽  
Single Epoch ◽  
Energy Survey

ABSTRACT We present new Gemini/GMOS optical spectroscopy of 16 extreme variability quasars (EVQs) that dimmed by more than 1.5 mag in the g band between the Sloan Digital Sky Survey (SDSS) and the Dark Energy Survey epochs (separated by a few years in the quasar rest frame). These EVQs are selected from quasars in the SDSS Stripe 82 region, covering a redshift range of 0.5 < z < 2.1. Nearly half of these EVQs brightened significantly (by more than 0.5 mag in the g band) in a few years after reaching their previous faintest state, and some EVQs showed rapid (non-blazar) variations of greater than 1–2 mag on time-scales of only months. To increase sample statistics, we use a supplemental sample of 33 EVQs with multi-epoch spectra from SDSS that cover the broad Mg ii λ2798 line. Leveraging on the large dynamic range in continuum variability between the multi-epoch spectra, we explore the associated variations in the broad Mg ii line, whose variability properties have not been well studied before. The broad Mg ii flux varies in the same direction as the continuum flux, albeit with a smaller amplitude, which indicates at least some portion of Mg ii is reverberating to continuum changes. However, the full width at half-maximum (FWHM) of Mg ii does not vary accordingly as continuum changes for most objects in the sample, in contrast to the case of the broad Balmer lines. Using the width of broad Mg ii to estimate the black hole mass with single epoch spectra therefore introduces a luminosity-dependent bias.

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